Modification of porous carbon with nitrogen elements to enhance the capacitance of supercapacitors

Abstract

A porous carbon precursor is prepared by modifying polyvinylidene fluoride with nitrogen via a chemical polyreaction and then introducing mesopores using the soft-template method. After carbonization at the appropriate temperature, the obtained carbon material could be applied in supercapacitors without further treatment. The resulting material exhibits not only a comparatively stable nitrogen content that is very close to the nitrogen content of its precursor but also an effective hierarchical porous structure (~ 0.68 and ~ 4 nm). The large specific surface area of the carbon material (up to 1688 m2 g−1) is also an important factor influencing its excellent electrochemical performance. When tested using 6 M KOH as an electrolyte in a three-electrode system, CN-900 exhibits a specific capacitance of 355.6 F g−1 at 1 A g−1. When tested using the same electrolyte in a two-electrode system, CN-900 shows a specific capacitance of 84.08 F g−1 at 0.5 A g−1. In addition, the carbon material can maintain 98.4% capacitance after 8000 charge/discharge cycles at a current density of 2 A g−1. The performance of CN-900 is further tested in a two-electrode solid-state supercapacitor with sulfuric acid/polyvinyl alcohol as the electrolyte, and a specific capacitance of 90.31 F g−1 is observed at 1 A g−1. Therefore, the nitrogen-modified porous carbon is a very promising material with practical applications in supercapacitors.